People get pretty excited when a manufacturer uses aluminum in the fabrication of a car. This metal is thought cutting edge, a product of the space age, and very advanced. Ferraris are made of aluminum, aircraft are made from aluminum and many racecars are made from aluminum. Manufacturers will often use aluminum for engine blocks or valve heads and these are usually promoted as far superior to cast iron and steel, and capable of higher performance. So people are often very surprised when I open the hood of a car built in the nineteen hundreds and show off an engine cast from aluminum, or when they see the polished aluminum bonnet of a 1914 Rolls Royce. Pierce Arrow, an American luxury car builder actually cast entire bodies from aluminum and just about all coach built cars built before the Second World War had a major percentage of their body components hand formed from sheet aluminum.
In the post war period aluminum fell into disuse as a material from which American cars were built although many European cars continued to use it extensively. American manufacturers re discovered aluminum when the weight of cars had to be reduced to meet fuel economy requirements. Aluminum weighs far less than steel or iron and although not as strong it can be made to work well in almost any application aside from combustion chambers.
The most common use for aluminum these days is in the after market production of dress up and performance parts. Billet aluminum is machine cut into almost everything from wheels to intake manifolds and billet has become a status symbol of sorts in Hot Rod circles. The more polished aluminum billet you have on the car the better.
The car manufacturers usually use cast aluminum components as billet is fairly expensive and requires a number of machines and operators to make the same form as can be done in one simple cast. In low production or custom production billet is the way to go but in mass quantities casting is much less expensive and far more efficient.
The last century saw powerful strides in metallurgy, with the most noticeable taking place during the Second World War. When carmakers first started using aluminum it was usually cast and rarely was the casting free of flaws.
Ettore Bugatti, the famous founder of the Bugatti Company who built some of the worlds finest cars in the twenties and thirties favored aluminum as a material because he had a passion for saving weight. While he was famous for the quality of the steels he used, the aluminum he incorporated into cars was so porous that engine blocks regularly sweat oil. Unlike most manufacturers even backing the twenties, Bugatti used a lot of billet in his cars because of limited production and the latitude that it gave him to create auto parts that were not only efficient but also beautiful to look at. His reasons were very similar to those of today's Hot Rodder.
Aluminum has not made a strong comeback as a material for car bodies. It has been used for exotic limited production cars such as Lamborghinis and Ferraris but never adopted for mass production aside from small panels. Lightweight composites, plastics and fiberglass are now used in place of aluminum for weight savings, durability and low production costs. Just about the only well known mass-produced post war vehicle that used aluminum for its body was the Landrover. I have owned several of these and it always amused me when people would assume it was indestructible and free of rust. While aluminum does not rust, it corrodes at an alarming rate, turning to a white powder and blowing away. In combination and in direct contact with steel, (a common design problem with the Landrover) it actually creates an electrical current, especially with salty water, which rapidly creates holes and structural problems. I owned one Landrover where an entire body section fell off on the highway one day. It is quite embarrassing having to pull over and retrieve a large section of your vehicle, especially when it has been run over a couple of times. A few Canadian winters and any unmaintained aluminum clad vehicle is quickly reduced to scrap.
While aluminum is not quite the miracle metal we would sometimes be led to believe, it does have many current applications in the automotive world. Modern technology will no doubt continue to refine it and I have no doubt that one day it will be found in forms even stronger than steel. It is in its essence however; still an invention of the eighteenth century and many of its uses have not changed all that dramatically. Modern manufacturers rarely use it anywhere on a car where it had not already been used by the year 1910.